No - how could it? In Java, overloading depends on the declared type of each parameter. In Ruby, parameters have no declared type. I suppose that the Ruby interpreter could allow overloading based only on the number of parameters, but it doesn't. Probably Matz didn't see a benefit to that, and so he kept a simpler model: there is only one method named digaMoo at a time, and when you declare the second version, it simply replaces the first.
I think the Ruby Way to handle this is to simply give the methods different names... like say_moo and say_moo_n_times, where the first expects no parameters, and the second expects one numeric parameter.
Ruby follows a different sort of OO implementation than Java. In Ruby, *everything* is an object. You don't have pseudo-objects like you do in java (int, char, long).
You communicate with objects via messages -- you send an object the message, either explicitly like foo.bar or implicitly like foo.send(:bar). The arguments are passed (ultimately) as an array. Most of the time you don't need to think of them being passed as such, but it's nice to have available, if needed. Since they're passed as an array, Ruby doesn't really care too much how many arguments are passed (unless you've declared that there are one or more arguments which do not have a default value).
Having the default value, like shown above, really makes more sense to me than overloading. I only need to look in one method to understand what's happening and I can easily create a default behaviour.
When Java came out, I thought it was great. I taught it for Sun for a while, too. My "dayjob" still uses it (at least a chunk of the time). But I've found Ruby to be "fun" and to increase my pleasure in coding.....